Ceramic composition

ABSTRACT

A colored ceramic body for use in various parts of electronic equipment, comprising at least one of A12O3 and BeO as a basic component, 0.1 to 5 percent by weight CoO and further additive chosen from the group consisting of MnO2, Cr2O3, V2O5, Fe2O3 and mixtures thereof, the total amount of CoO and further additive being 1.0 to 10 percent by weight. The ceramic body is dark in color and has excellent electrical, mechanical and thermal characteristics, and maintains an acceptably high volume resistivity even after the body has been heated in a reducing atmosphere.

United States Patent Sugiura et a1.

CERAMIC COMPOSITION Filed: Jan. 27, 1972 Appl. No.: 221,267

Related U.S. Application Data Continuation-in-part of Ser. No. 864,178, Oct. 6, 1969, abandoned.

Foreign Application Priority Data Oct. 18, 1968 Japan 43-76218 U.S. Cl 106/46, 106/39.5, 106/73.33,

106/73.4, 106/65 Int. Cl C04b 33/26 Field of Search..... 106/46, 45, 39, 65, 73.4, 42

References Cited UNITED STATES PATENTS 5/1969 Berghezan 106/65 X Feb. 12, 1974 1,775,867 9/1930 Sandmeier 106/42 2,427,454 9/1947 Heany 106/42 3,345,596 10/1967 Delaney et a1 252/518 X 3,446,669 5/1969 Arrance et a1 106/65 X 2,152,656 4/1939 McDougal et al. 106/46 X 1,633,462 6/1927 Sortwell 106/46 2,413,441 12/1946 Feichtcr 106/46 X 3,291,619 12/1966 Luks 106/46 2,982,664 5/1961 Luks 106/65 X Primary Examiner-Helen M. McCarthy Attorney, Agent, or Firm-Christensen, OConnor, Garrison & Havelka 5 7 ABSTRACT A colored ceramic body for use in various parts of electronic equipment, comprising at least one of A1 0 and BeO as a basic component, 0.] to 5 percent by weight COC and further additive chosen from the group consisting of MnO Cr O V 0 Fe O and mixtures thereof, the total amount of C00 and further additive being 1.0 to 10 percent by weight. The ceramic body is dark in color and has excellent e1ectri cal, mechanical and thermal characteristics, and maintains an acceptably high volume resistivity even after the body has been heated in a reducing atmosphere.

' 5 Claims, N0 Drawings 1 CERAMIC COMPOSITION CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of U. S. Ser. No. 864,178, filed Oct. 6, 1969, now abandoned, entitled CERAMIC COMPOSITION, inventor, Masatoshi Sugiura et al.

This invention relates to a colored ceramic body for use in various parts of electronic equipment.

It is required that ceramic material used in various electronic parts such as semi-conductor IC packages, transistor headers, etc. should have good electrical insulation characteristic, high mechanical strength and high thermal conductivity. Alumina and beryllia are known as the substances that meet the above requirements and have been shown in the literature and by examples below to be equivalent and interchangeable.

In some applications of the ceramic material, it is further required that they should also have a high degree of heat emissivity so that a large amount of heat may not be stored in theceramic body, and that the ceramic body should be opaque so that no light is transmitted therethrough. To meetthe requirements, it is common practice to color the ceramic body to black or nearblack by adding thereto suitable metal oxides as coloring agents. g Q

In electronics, the ceramic bodies are usually sealed to metals. In such a case, the surface of the ceramic body is first metallized and then adhered to the metal by means of brazing. In the metallizing and brazing processes, it is required that the processes should be carried out in a reducing atmosphere in order to prevent the oxidization of the metal. As mentioned above, however, the ceramic body contains various metal oxides as coloring agents, so that in the reducing atmosphere the oixides'are reduced, thereby deteriorating the volume resistivity and thereby the insulating property of the ceramic body. l-Ieretofore, such deterioration has been considered inevitable and the problem has been left unsolved.

Accordingly, the primary object of the invention is to provide a colored ceramic body for usein various electronic parts, which has excellent electrical, mechanical and thermal characteristics, and in which the volume resistivity is not deteriorated when the ceramic body has been treated in a reducing atmosphere.

Another object of the invention is to provide a colored ceramic body for use in various electronic parts, which comprises at least one of alumina and beryllia as a basic component, an essential additive of cobalt oxide 0.1 to 5.0 percent by weight (the percentages throughout the specification and claims will be by weight), and a further additive consisting of at least one of manganese oxide 0.1 to 5.0 percent, chrome oxide 0.] to 5.0 percent, vanadium oxide 0.1 to 2.0 percent and iron oxide 0.1 to 2.0 percent, the total of CO and further additive being 1.0 to percent by weight, said materi als being sintered.

The ceramic products obtained in accordance with the invention are all dark in color such as brown or dark brown, which colors are satisfactory in practical use, and have a relatively high volume resistivity of 10 to 10 ohm/cm, which value can be substantially retained even after the products have been exposed to a reducing atmosphere.

It should be noted that if the above-stated metal oxides are added in an amount exceeding the above specified ranges of percentage, the electrical, mechanical and thermal characteristics inherent in alumina and/or beryllia are deteriorated, while if they are added in an amount less than the specified ranges, sufficient coloration cannot be accomplished.

The reason why the ceramic body composed in accordance with the invention can retain its excellent resistivity even after it has been treated in a reducing atmosphere is considered as follows: When the raw batch prepared in accordance with the invention are fired to the sintering temperature, the metal oxides including cobalt oxide 0.1 to 5.0 percent as an essential additive go into solid solution with the alumina, Beryllia or mixtures thereof with a considerable part of them forming a stable matrix phase in the ceramic body, which suppresses the reducing action. The co-existence of cobalt oxide and the mentioned other metal oxide or oxides helps promote the formation of the stable matrix phase. There results a ceramic having a volume resistivity which is not deteriorated when the ceramic is heated in a reducing atmosphere.

To put it in more detail, when the raw batch, including alumina and/or beryllia as the principal components with an essential additive of 0.1 to 5.0 percent by weight COO with other metal oxide coloring agents in the amounts as defined in the appended claims, the metal oxides go into solid solution with the alumina and/or beryllia as stable oxides. It is well known in the art that the oxygen atoms in a solid solution are far less likely to be reduced than free oxygen atoms in the matrix of a ceramic material. Thus, the ceramics of this invention are much less prone to lose oxygen atoms by reduction in a heated reducing atmosphere and thereby become semi-conductive. The present invention defines the relative percentage ranges of the components which accomplishes the desired result. If the ranges of the listed constituents are not observed it is theorized that the excess metal oxides leave in the ceramic matrix free oxygen atoms which are more likely to be reduced, thereby rendering the ceramic semi-conductive and thereby deteriorating its electrical resistance. On the contrary, if the essential ingredient of CO0 is absent with only the coloring agents well known in the prior art, no such stable solid solution matrix phase is formed. Such prior art ceramics readily lose oxygen atoms when heated in a reducing atmosphere thereby lowering the resistivity to an unacceptable level for use as an electronic component.

The invention will be further described with reference to some specific examples which are given for purposes of illustration only and are not to be taken in any way restricting the invention.

in theprior art.

other oxides is 1.0 to 5.0 percent by weight and preferably 1.5 to 4.0. Sample numbers and l 1 clearly show h p stsrrss 92WB9EE1Q1LE1S2099;-

TABLE 1 COMPONENTS SAMPLE A1 0 96.0 96.0 83.0 95.3 93.0 90.0 91.0 33.4 92.4 92.0 Be() 97.0 10.0 60.0 COO 0.3 0.5 3.0 0.4 1.0 0.5 0.8 0.1 5.0 MnO, 1.0 0.7 0.5 2.0 2.0 3.0 3.7 3.0 3.5 0.5 C 0: 2.0 2.0 2.0 1.0 2.1 1.0 2.5 1.0 V 0 0.3 0.5 0.3 0.2 Fe O 1.0 0.5 1.0 0.8 2.5 2.0 0.2 1.5 SiO 0.5 1.2 0.4 0.3 TiO 2.0 1.0 2.0 0.7 1.5 MgO l 0 2.0 NiO 1.0 0.2 CuO 1.0 0.2 COLOR dark brown blue dark brownbrwnblk. blk. dark Blk. dark brown black blue ish ish brwn. blue FIRING black blk.

TIME (Hr.) 2 2 2 2 2 2 2 2 2 2 2 The compositions shown in Table l are batch compositions using chemically pure inorganic materials which are commercially available. The resulting ceramic solid solution formed upon firing of these batch compositions were found to be substantially identical in composition to-the batch composition utilized. if it is desired to use less pure inorganic materials it will be necessary to adjust the batch compositions to result in a final fired Table 11 below shows the firing temperatures at which the samples were sintered, thevolume resistivity of the samples after the sintering, the temperatures at which the ceramic bodies were heated for 2 hours in a reducing atmosphere and their volume resistivity after the heat treatment. in this table, the temperatures are given in centigrades and the resistivity is in ohm/cm measured at 2 0O "C ceramic composition in the desired ranges. Best results will be obtained through usage of the chemically pure raw materials to avoid the introduction of undesirable impurities detrimental to the electrical properties of the resulting fired ceramic. By usage of pure raw materials batch compositions will be very closely equal to analyzed compositions of the fired product.

The total amount of the essential ingredient C00 in combination with other metal oxides is in the range of approximately 1.0 to 10 percent by weight and preferably is in the range of 1.5 to 9 percent. The preferred range of C00 is 0.1 to 3.0 percent by weight. The major constituent, A1 0 BeO or mixtures thereof is present in the range of 85 to 99 percent and preferably 90 to 98.5 percent by weight.

When the amount of C00 is approximately 0.1 percent, the amount of the other metal oxides is in the range of 1.5 to 10 percent by weight and preferably is in the range of 2.0 to 9.0 percent. When the amount of C99 i tb nssqf -llps s the wn!" of th As is clearly seen from Tables I and 11 all the samples are dark color and in Sample No. 1 and No. 6 which do not contain any cobalt oxide (prior art compositions) the volume resistivities are 10" and 10 ohm/cm after. the firing, but are greatly reduced to 10 ohm/cm after they are further heated in a reducing atmosphere. Exceptionally, Sample No. 7 which contains a relatively large amount (3 percent in all) of titanium oxide, nickel oxide and copper oxide also has its volume resistivity greatly reduced by the treatment in the reducing atmosphere, whereas no such reduction of the volume resistivity has been observed in Sample Nos. 8 and 9 which contain a relatively small amount (less than 2.5 percent in all) of these compounds. Sample Nos. 2 to 5, 8, 9, l0 and l 1 prepared in accordance with the invention retain their respective high volume resistivities substantially unchanged before and after the heat treatment in the reducing atmosphere.

The cobalt oxide not only serves to color the ceramic bodies but also helps prevent the reduction of the ox- 1 ides in -the reducing atmosphere. Therefore, the cobalt oxide is an essential component of the ceramic body of the invention. With respect 'to the other metal oxides serving as a coloring agent, that is, the oxides of manganese, chromium, vanadium, iron, titanium, nickel and copper, generally the presence of the e o lo r ing agents other than the chrome oxide is likely to promote crystal growth in the ceramic body, thereby deteriorating the electrical and mechanical properties of the sintered ceramic body, that is reducing the mechanical strength and the electrical resistance. The chrome oxide is effective in suppressing the crystal growth and therefore is preferably added in addition to the cobalt oxide. The oxides of manganese, vanadium, iron, titanium, and copper are effective in promoting sintering and may be added in a suitable amount depending on specific sintering conditions. However, if the oxides of titanium, copper or nickel are added in a large amount, they will cause the reduction of the resistivity of the ceramic body, because those oxides are apt to be reduced especially by the heat treatment in the reducing atmosphere. Therefore, the total amount of these oxides to be added must not exceed about 2.5 percent.

Titanium oxide alone is white or yellow in color in an oxidizing atmosphere and therefore cannot be used as a coloring agent. However, if it coexists with manganese oxide or iron oxide, it helps color the ceramic body to the dark colors.

It should be noted that besides the above-mentioned coloring agents, MgO, CaO, D0,, or other mineralizers, which are non-coloring agents, may also be added in small quantities so long as they do not adversely affect the effects of the invention. Impurities such as alkali metal oxides may exist in the ceramic body. Of course, the impurities must be minimized.

What we claim is:

l. A fired ceramic body having a bulk resistivity in the range of 10 to 10 ohm/cm at 200C., said bulk resistivity being relatively unaffected by exposure of said ceramic to reducing atmospheres at elevated temperatures consisting essentially of at least percent by weight of an oxide chosen from the group consisting of A1 0 BeO and mixtures thereof combined in solid solution with 0.1 to 5.0 percent by weight C00 and a component chosen from the group consisting of at least one of 0.1 to 5.0 percent MnO,, 0.1 to 5.0 percent Cr o 0.1 to 2.0 percent V 0 and 0.1 to 5.0 percent Fe,O the total amount of C00 and said component being 1.0 to 10 percent by weight, said body being colored and opaque to light.

2. The ceramic body of claim 1 wherein C00 is present in the amount of 0.1 to 3.0 percent by weight.

3. The ceramic body of claim 1 consisting essentially of approximately 97.0 percent by weight BeO, 0.3 percent by weight CoO, 0.7 percent by weight MnO 0.5 percent by weight Fe O 0.5 percent by weight SiO, and 1.0 percent by weight MgO.

4. The ceramic body of claim 1 consisting essentially of approximately 95.3 percent by weight A1 0 0.4 percent by weight C0D, 2.0 percent by weight MnO 2.0 percent by weight Cr O and 0.3 percent by weight V 0 5. The ceramic body of claim 1 consisting essentially of approximately 91.0 percent by weight M 0 0.5 percent by weight C00, 3.7 percent by weight MnO 2.1 percent by weight Cr O 0.3 percent by weight V 0 0.4' percent by weight SiO and 2.0 percent by weight TiO 

2. The ceramic body of claim 1 wherein CoO is present in the amount of 0.1 to 3.0 percent by weight.
 3. The ceramic body of claim 1 consisting essentially of approximately 97.0 percent by weight BeO, 0.3 percent by weight CoO, 0.7 percent by weight MnO2, 0.5 percent by weight Fe2O3, 0.5 percent by weight SiO2 and 1.0 percent by weight MgO.
 4. The ceramic body of claim 1 consisting essentially of approximately 95.3 percent by weight Al2O3, 0.4 percent by weight CoO, 2.0 percent by weight MnO2, 2.0 percent by weight Cr2O3 and 0.3 percent by weight V2O5.
 5. The ceramic body of claim 1 consisting essentially of approximately 91.0 percent by weight Al2O3, 0.5 percent by weight CoO, 3.7 percent by weight MnO2, 2.1 percent by weight Cr2O3, 0.3 percent by weight V2O5, 0.4 percent by weight SiO2, and 2.0 percent by weight TiO2. 